Neisseria gonorrhoeae is the etiologic agent of gonorrhea, one of the most prevalent infectious diseases in the U.S. Complications of gonorrhea include pelvic inflammatory disease (PID), the leading cause of sterility in females in this country. Despite the ability to effectively treat gonorrhea with antibiotics, the incidence of this disease remains high, suggesting that the most likely means of controlling the epidemic in the U.S. will be by vaccination. Elimination of gonorrhea will require an understanding of the host immune response to and pathogenesis of N. gonorrhoeae. One of the central themes of microbial pathogenesis is that the pathogen may express virulence determinants in vivo that are not expressed in vitro. We have been investigating the regulation of gonococcal gene expression by anaerobiosis, an environmental condition that this pathogen is likely to encounter in vivo in females. We have identified two anaerobically induced genes, ani A and norB, that are induced anaerobically and encode nitrite reductase and nitric oxide reductase, respectively. Both of these proteins are required for anaerobic growth and their presence means that gonococci can both produce and degrade nitric oxide (NO), an important modulator of the host innate immune response. We propose 1) to perform genetic and biochemical analyses of anaerobically regulated genes; 2) to determine the role of anaerobically induced and repressed genes in gonococcal invasion via the lutropin receptor; 3) to determine steady state NO concentrations during gonococcal denitrification and the effect of environmental parameters; and 4) to determine if gonococcal production/degradation of NO and/or steady-state NO levels down regulate cytokine expression and activation of soluble guanylyl cyclase. The successful completion of these aims should provide important new information on the function of the denitrification pathway and its role in pathogenesis. In addition, significant new insights into the mechanism of gonococcal suppression of the innate immune response may be attained. [unreadable] [unreadable]